Method and apparatus for performing an open wedge, high tibial osteotomy

ABSTRACT

Apparatus for performing an open wedge, high tibial osteotomy, the apparatus comprising: a wedge-shaped implant for disposition in a wedge-shaped opening created in the tibia, wherein the wedge-shaped implant comprises a hole extending therethrough; a fixation screw for extending through the hole and securing the wedge-shaped implant to the tibia; and a locking mechanism for releasably locking the fixation screw to the wedge-shaped implant. The fixation screw comprises: a shaft having a distal threaded portion and a proximal threaded portion, wherein the distal threaded portion and the proximal threaded portion are characterized by different thread pitches.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application:

(i) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/047,159, filed Jan. 31, 2005 by Vincent P. Novak for OPENWEDGE OSTEOTOMY SYSTEM AND SURGICAL METHOD;

(ii) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/047,551, filed Jan. 31, 2005 by Vincent P. Novak for OPENWEDGE OSTEOTOMY SYSTEM AND SURGICAL METHOD;

(iii) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/352,103, filed Feb. 9, 2006 by Vincent P. Novak et al. forMULTI-PART IMPLANT FOR OPEN WEDGE KNEE OSTEOTOMIES;

(iv) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/350,333, filed Feb. 8, 2006 by Vincent P. Novak et al. forMETHOD AND APPARATUS FOR FORMING A WEDGE-LIKE OPENING IN A BONE FOR ANOPEN WEDGE OSTEOTOMY;

(v) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/396,490, filed Apr. 3, 2006 by Kelly Ammann et al. forMETHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY;

(vi) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/607,321, filed Dec. 1, 2006 by Kelly G. Ammann et al. forMETHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY;

(vii) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 11/644,218, filed Dec. 22, 2006 by Kelly G. Ammann et al. forMETHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY;

(viii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/835,172, filed Aug. 2, 2006 by Kelly G. Ammannet al. for METHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGEOSTEOTOMY;

(ix) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,269, filed Aug. 3, 2006 by Kelly G. Ammann et al. forMETHOD AND SYSTEM OF FIXATION FOR PERFORMING AN OPENING WEDGE OSTEOTOMY;

(x) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,292, filed Aug. 3, 2006 by Robert E. Schneider et al.for BONE ANCHOR FOR FIXATION TO A DISTAL CORTICAL WALL THROUGHCANCELLOUS BONE;

(xi) claims benefit of pending prior U.S. Provisional Patent ApplicationSer. No. 60/835,268, filed Aug. 3, 2006 by Kelly G. Ammann et al. forOPEN WEDGE OSTEOTOMY SYSTEM;

(xii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/847,527, filed Sep. 27, 2006 by Vincent P. Novaket al. for KEYHOLE OSTEOTOMY SYSTEM; and

(xiii) claims benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/860,595, filed Nov. 22, 2006 by Kelly Ammann etal. for METHOD AND APPARATUS FOR PERFORMING AN OPEN WEDGE, HIGH TIBIALOSTEOTOMY.

The thirteen (13) above-identified patent applications are herebyincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to surgical methods and apparatus in general, andmore particularly to surgical methods and apparatus for performing openwedge, high tibial osteotomies of the knee.

BACKGROUND OF THE INVENTION

Osteotomies of the knee are an important technique for treating kneeosteoarthritis. In essence, knee osteotomies adjust the geometry of theknee joint so as to transfer weight bearing load from arthritic portionsof the joint to relatively unaffected portions of the joint.

Knee osteotomies are also an important technique for addressing abnormalknee geometries, e.g., due to birth defect, injury, etc.

Most knee osteotomies are designed to modify the geometry of the tibia,so as to adjust the manner in which the load is transferred across theknee joint.

There are essentially two ways in which to adjust the orientation of thetibia: (i) the closed wedge technique; and (ii) the open wedgetechnique.

With the closed wedge technique, a wedge of bone is removed from theupper portion of the tibia, and then the tibia is manipulated so as toclose the resulting gap, whereby to reorient the lower portion of thetibia relative to the tibial plateau and hence adjust the manner inwhich load is transferred from the femur to the tibia.

With the open wedge technique, a cut is made into the upper portion ofthe tibia, the tibia is manipulated so as to open a wedge-like openingin the bone, and then the bone is secured in this position (e.g., byscrewing metal plates to the bone or by inserting a wedge-shaped implantinto the opening in the bone), whereby to reorient the lower portion ofthe tibia relative to the tibial plateau and hence adjust the manner inwhich load is transferred from the femur to the tibia.

While both closed wedge osteotomies and open wedge osteotomies providesubstantial benefits to the patient, they are procedurally challengingfor the surgeon. Among other things, with respect to open wedgeosteotomies, it can be difficult to create the wedge-like opening in thebone with the necessary precision and with a minimum of trauma to thesurrounding tissue (e.g., the neurological and vascular structures atthe back of the knee). Furthermore, with open wedge osteotomies, it canbe difficult to stabilize the upper and lower portions of the tibiarelative to one another and to maintain them in this position whilehealing occurs.

The present invention is directed to open wedge, high tibial osteotomiesof the knee, and is intended to provide increased precision and reducedtrauma when creating the wedge-shaped opening in the bone, and toprovide increased stability to the upper and lower portions of the tibiawhile healing occurs.

SUMMARY OF THE INVENTION

The present invention comprises a novel method and apparatus forperforming an open wedge, high tibial osteotomy. More particularly, thepresent invention comprises the provision and use of a novel method andapparatus for forming an appropriate osteotomy cut into the upperportion of the tibia, manipulating the tibia so as to open anappropriate wedge-like opening in the tibia, and then mounting anappropriately-shaped implant at the wedge-like opening in the tibia, soas to stabilize the tibia with the desired orientation, whereby toreorient the lower portion of the tibia relative to the tibial plateauand hence adjust the manner in which load is transferred from the femurto the tibia.

In one form of the present invention, there is provided apparatus forperforming an open wedge, high tibial osteotomy, the apparatuscomprising:

a wedge-shaped implant for disposition in a wedge-shaped opening createdin the tibia, wherein the wedge-shaped implant comprises a holeextending therethrough;

a fixation screw for extending through the hole and securing thewedge-shaped implant to the tibia; and

a locking mechanism for releasably locking the fixation screw to thewedge-shaped implant.

In another form of the present invention, there is provided apparatusfor performing an open wedge, high tibial osteotomy, the apparatuscomprising:

a fixation screw for securing an implant to the tibia, the fixationscrew comprising:

a shaft having a distal threaded portion and a proximal threadedportion, wherein the distal threaded portion and the proximal threadedportion are characterized by different thread pitches.

In another form of the present invention, there is provided apparatusfor performing an open wedge, high tibial osteotomy, the apparatuscomprising:

a fixation screw for securing an implant to the tibia, the fixationscrew comprising:

a shaft having a distal threaded portion and a proximal threadedportion, wherein the distal threaded portion and the proximal threadedportion are characterized by different thread heights.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts, and further wherein:

FIGS. 1-3 are schematic views of the left leg from an anterior view,showing the formation of a wedge-like opening in the tibia for an openwedge, high tibial osteotomy, and positioning of a wedge-shaped implantinto the wedge-like opening in the tibia;

FIG. 3A is a schematic view showing selected anatomical body planes;

FIGS. 4-9 show the relevant planar surfaces in an open wedge, hightibial osteotomy conducted in accordance with the present invention fromthe anterior view and the medial view of the left leg;

FIGS. 10-30 are schematic views showing a preferred method and apparatusfor forming an appropriate osteotomy cut into the upper portion of thetibia, manipulating the tibia so as to open an appropriate wedge-likeopening in the tibia, and then inserting an appropriate wedge-shapedimplant into the wedge-like opening in the tibia;

FIGS. 31-33 are schematic views showing an alternative wedge-shapedimplant also formed in accordance with the present invention;

FIG. 34 is a schematic view showing a keyhole drill guide which may beused in conjunction with the wedge-shaped implant shown in FIGS. 31-33;

FIG. 35 is a schematic view showing another wedge-shaped implant formedin accordance with the present invention;

FIGS. 36-38 are schematic views showing still another wedge-shapedimplant formed in accordance with the present invention;

FIGS. 39-41 are schematic views showing a keyhole drill guide and an endmill which may be used in conjunction with the wedge-shaped implantshown in FIGS. 36-38;

FIGS. 42-44 are schematic views showing yet another wedge-shaped implantformed in accordance with the present invention;

FIGS. 45-47 are schematic views showing another wedge-shaped implantformed in accordance with the present invention;

FIGS. 48-50 are schematic views showing still another wedge-shapedimplant formed in accordance with the present invention;

FIGS. 51-56 are schematic views showing a one-piece implant with lockingfixation screws; and

FIGS. 57-66 are schematic views showing fixation screws for improvedengagement with both cortical and cancellous bone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overview of an OpenWedge, High Tibial Osteotomy

Looking first at FIGS. 1-3, there is shown a knee joint 5 of, forexample, the left leg from an anterior view upon which an open wedgeosteotomy is to be performed. Knee joint 5 generally comprises a tibia10 and a femur 15. In accordance with the present invention, the openwedge osteotomy is effected by first making a cut 20 (FIG. 1) into theupper tibia, and then manipulating the lower portion of the tibia so asto open a wedge-like opening 25 (FIG. 2) in the bone, with thewedge-like opening 25 being configured so as to adjust the manner inwhich load is transferred from the femur to the tibia. In this respect,it should be appreciated that a variety of methods are well known in theart for determining the degree of correction necessary to correctlyre-align the weight-bearing axis of the knee. Furthermore, cut 20 andwedge-like opening 25 may be formed in a variety of ways well known inthe art.

Among other things, the present invention provides a new and improvedmethod and apparatus for forming cut 20 and wedge-like opening 25, aswill be discussed in detail below.

Once the desired wedge-like opening 25 has been formed in tibia 10 so asto reconfigure tibia 10 to the desired geometry, the bone may be securedin position in a variety of ways well known in the art (e.g., byscrewing metal plates to the bone or by inserting a wedge-shaped implantinto the opening in the bone), whereby to adjust the manner in which theload is transferred from the femur to the tibia. By way of example, FIG.3 shows a wedge-shaped implant 27 inserted into the wedge-like opening25 formed in the tibia, whereby to stabilize the tibia in itsreconfigured geometry.

Among other things, the present invention also provides a new andimproved implant, and an associated method and apparatus for deployingthe same at the wedge-shaped opening in the tibia, as will be discussedin detail below.

Discussion of the Relevant Planar Surfaces in the Open Wedge, HighTibial Osteotomy of the Present Invention

In order to appreciate certain aspects of the present invention, it ishelpful to have a thorough understanding of the planar surfaces of thetibia that are relevant in performing the open wedge, high tibialosteotomy of the present invention. Thus, the following discussionpresents a geometric description of the planar surfaces that arerelevant to the open wedge, high tibial osteotomy of the presentinvention. For the purposes of the present discussion, it can sometimesbe helpful to make reference to selected anatomical planes, e.g., thesagittal plane 1, the coronal plane 2 (also known as the frontal plane),and the transverse plane 3 (FIG. 3A).

Looking now at FIGS. 1-4, for the purposes of the present invention, thetibial plateau 30 may be described as a horizontal (or transverse) planethat extends along the top surface of tibia 10. For reference andexample, FIG. 4 shows the left leg from an anterior view such that themedial side 6 and the lateral side 7 of the tibia 10 can be seen. Thesagittal plane 32 is also shown in FIG. 4. As seen in FIG. 5 from themedial view, tibial plateau 30 is also perpendicular to the frontal (orcoronal) plane 40. The anterior-posterior (A-P) slope is defined by ananterior-posterior (A-P) slope plane 45 that extends along the slopingtop surface of the tibia, from anterior side 12 to posterior side 10.Published research has demonstrated that the anterior-posterior (A-P)slope typically extends at an exemplary angle 13 of approximately 7° to11° to the tibial plateau 30; however, the specific angle may vary fromindividual to individual.

Looking next at FIG. 6, a medial view of the left leg, for the openwedge, high tibial osteotomy of the present invention, it is generallydesirable to stay an exemplary distance 14 of about 2 cm inferior to theA-P slope plane 45. This offset can be referred to as the A-P offsetplane 50.

As seen in FIG. 7, an anterior view of the left leg, the lateral aspectand cut depth of the cut 20 may be defined by a lateral aspect plane 55and a cut depth plane 60, with the cut depth being an exemplary distance15 of about 1 cm toward the medial side 6 from the lateral aspect plane55 of the tibia, located on the lateral side 7 of the tibia.

Looking next at FIG. 8, showing the left leg from an anterior view, theosteotomy cut plane 65 (when seen from the direct frontal view of FIG.8) is formed by a plane that is rotated away from the A-P offset plane50 through an axis which is formed by the intersection of the cut depthplane 60 and the A-P offset plane 50. The degree of rotation is selectedso as to be sufficient to place the entry of the osteotomy cut plane 65at the medial neck 66 (FIG. 8) of the tibia. It should be noted that theA-P offset plane 50 and the osteotomy cut plane 65 are “tilted” slightlyfrom anterior to posterior (but not seen in the direct frontal view ofFIG. 8), since the A-P offset plane 50 and the osteotomy cut plane 65follow the tilt of the A-P slope plane 45 (FIG. 6). The intersection ofthe A-P offset plane 50 and the cut depth plane 60 forms an axis 70which, in accordance with the present invention, defines the laterallimit of the osteotomy cut 20. In other words, axis 70 defines a linethrough the tibia which is (i) parallel to A-P slope plane 45, and (ii)contained within osteotomy cut plane 65. Furthermore, in accordance withthe present invention, axis 70 is used to define the lateral limit ofthe osteotomy cut 20 which is to be made into the tibia.

FIG. 9 is a direct view taken along the osteotomy cut plane, showing theleft leg from an anterior view tilted slightly superior. This view istilted downward (e.g., at an angle of approximately 7° from the directfrontal view of FIG. 8. Again, the angle of tilt downward is equal tothe A-P slope. In other words, with the present invention, the osteotomycut plane 65 extends parallel to the A-P slope plane 45 (in theanterior-to-posterior direction, although not in the medial-to-lateraldirection), and typically slopes downward (e.g., at an angle ofapproximately 7-11°) when viewed in the anterior-to-posterior direction.Furthermore, with the present invention, the axis 70 (which defines thelateral limit to the osteotomy cut 20) is contained within the osteotomycut plane 65.

Novel Method and Apparatus for Performing the Open Wedge, High TibialOsteotomy of the Present Invention

In one preferred embodiment of the present invention, there is provideda novel osteotomy system which comprises instrumentation for use inmaking precise and repeatable osteotomy cuts for use in open wedge, hightibial osteotomies, preferably using an antero-medial approach. Thenovel osteotomy system generally comprises a positioning guide 100 (FIG.16), a slope guide 200 (FIG. 11), an apex pin 300 (FIG. 16), a keyholedrill guide 400 (FIG. 18), a posterior protector 500 (FIG. 20), and acutting guide 600 (FIG. 20), as will hereinafter be discussed in furtherdetail.

The novel osteotomy system preferably also comprises a novel openingjack 700 (FIG. 22) for opening the cut 20 in the tibia so as to form thewedge-like opening 25 in the tibia, as will also hereinafter bediscussed in further detail.

And the novel osteotomy system preferably also includes a novel implant800 (FIG. 24) for positioning in the wedge-like opening in the tibia soas to stabilize the tibia in its corrected configuration, as will alsohereinafter be discussed in further detail. Furthermore, in someinstances, it may be advantageous to use an implant trial base 830(FIGS. 27 and 28) in the course of preparing the tibia to receiveimplant 800, and in order to confirm proper fit of implant 800 in itsseat, as will also hereinafter be discussed in further detail.

Thus, with the present invention, the surgeon first determines (usingmethods well known in the art) the degree of correction necessary tocorrectly re-align the weight-bearing axis of the knee; then the surgeonuses the system to make the appropriate cut 20 into the tibia; then thesurgeon opens the bone cut to the extent required so as to form thedesired wedge-like opening 25 in the tibia; and then the surgeonstabilizes the tibia in its corrected configuration (e.g., with thenovel implant 800) while healing occurs.

In a preferred form of the invention, the novel osteotomy system isconfigured so that:

(i) the axis 70 (FIG. 8) formed at the lateral limit of the osteotomycut 20 (which forms the lateral limit of the remaining bony hinge whenthe osteotomy cut 20 is thereafter opened) is parallel to the A-P tibialslope;

(ii) the axis of the lateral limit of the bony hinge created by theosteotomy cut lies in a plane that is perpendicular to the frontal(i.e., coronal) plane; and

(iii) when the osteotomy cut 20 is completed and the wedge is opened,the distal (i.e., lower) tibia is rotated about the bony hinge so as tosubstantially maintain, in anatomical alignment, the A-P slope and thefrontal plane.

In a preferred form of the invention, the novel osteotomy system is alsoconfigured so that:

(iv) the osteotomy can be performed less invasively; and

(v) the osteotomy can be performed with minimum incising of soft tissuesuch as the medial collateral ligament, the lateral collateral ligament,and the hamstrings.

In a preferred form of the invention, the novel osteotomy system is alsoconfigured so that the delicate neurological and vascular tissues at theback of the knee are fully protected during the osteotomy procedure.

In one preferred form of the present invention, the novel osteotomysystem is constructed and used as follows.

A vertical incision is first made on the antero-medial portion of theknee, approximately 1 cm from the medial edge of the patellar tendon,with the incision beginning approximately 2.5-3 cm superior to theanterior tibial tubercle, and extending approximately 6-10 cm in length.

The soft tissue between the patellar tendon and the proximal surface ofthe tibia is then dissected in order to make a small tunnel-like openingbeneath the patellar tendon, just above the patellar tendon's insertionto the proximal tibia.

Looking now at FIG. 10, an assembly comprising positioning guide 100(FIGS. 10 and 16), slope guide 200 (FIGS. 10 and 11) and an introducer105 (FIGS. 10 and 11) is advanced to the surgical site. FIG. 10 showsthe tibia 10 oriented such that the left leg is seen with the medialside 6, lateral side 7, posterior side 11, and anterior side 12 asshown. Preferably, the assembly of positioning guide 100, slope guide200 and introducer 105 is pre-assembled prior to opening the skin. Thisassembly is assembled by first mounting slope guide 200 to positioningguide 100, and then mounting introducer 105 to both slope guide 200 andpositioning guide 100 by using a screw 115 (FIG. 10) which passesthrough slope guide 200 and is received in a threaded bore 120 (FIG. 16)formed in positioning guide 100.

In one preferred form of the invention, slope guide 200 may comprise twoseparate elements which are secured together, e.g., a base 210 and aguide element 215 which are connected together by pins 205, with base210 being formed out of a radio-translucent material (e.g., plastic) andguide element 215 being formed out of a radio-opaque material (e.g.,stainless steel), whereby guide element 215 will be visible underfluoroscopy and base 210 will be effectively invisible underfluoroscopy, as will hereinafter be discussed.

In one preferred form of the invention, introducer 105 may comprise anarm 125 and a handle 130. Arm 125 and handle 130 may be formed as twoseparate elements secured together, or arm 125 and handle 130 may beformed as a singular construction.

Next, the foregoing assembly (of positioning guide 100, slope guide 200and introducer 105) is maneuvered so that a tibial tubercle locating tab135 (FIGS. 10 and 16) of positioning guide 100 is inserted between thepatellar tendon (not shown) and the tibia, and so that tibial tuberclelocating tab 135 is set against the superior margin of the tibialtubercle. In this way, the tibial tubercle provides a rough alignmentguide for aligning positioning guide 100 with the tibia. If desired, theunderside of tibial tubercle locating tab 135 may include serrations138, ridges, ribs, etc. (FIGS. 11D and 11E) so as to facilitatestabilization of tibial tubercle locating tab 135 (and hence theinstrumentation) against the tibia.

Using a lateral fluoroscope view, taken from the medial side at thelevel of the tibial plateau, the assembly is then aligned so that theunderside surface 220 (FIG. 11) of guide element 215 of slope guide 200is aligned with the top of the medial condyle 75 of the tibia.Alternatively, if the surgeon prefers to shift the osteotomy slightlydistally on the tibia, the top edge 225 of guide element 215 of slopeguide 200 can be aligned with medial condyle 75, thereby offsetting theosteotomy by a fixed distance distally (e.g., 3 mm).

By forming the guide element 215 of slope guide 200 out of aradio-opaque material and by forming the base 210 of slope guide 200 outof a radio-translucent material, base 210 will be effectively invisibleunder fluoroscopy and guide element 215 will stand out in clear reliefagainst the bone.

It should be noted that guide element 215 of slope guide 200 ispreferably formed with a “Z shape” (FIGS. 10 and 11A) so as to provideadditional functionality. More particularly, by forming guide element215 with a “Z shape”, several significant advantages are obtained.First, this construction permits guide element 215 to wrap around theperimeter of the tibia. Second, the “Z shape” of guide element 215 alsooperates to indicate if the slope guide is not vertically aligned withthe level of the fluoroscope. More particularly, if, as shown from alateral view, the slope guide 200 is not vertically aligned with thelevel of the fluoroscope, the “Z shape” of guide element 215 will appearas a jagged or zig-zag shape on the fluoroscope (FIG. 11B). However, ifguide element 215 is vertically aligned with the level of thefluoroscope, then the guide element will appear as a straight line onthe fluoroscope (FIGS. 11 and 11C). This vertical alignment isimportant, since it enables alignment of slope guide 200 (and hencepositioning guide 100) with the medial condyle, i.e., with the A-P slopeplane.

If desired, and looking now at FIG. 11D, showing the position guide 100,slope guide 200, and introducer 105, 11E, showing the tibia tuberclelocating tab 135 and serrations 138, and 11F, showing the slope guide200 aligned with the anterior-posterior slope, it is also possible toprovide guide element 215 of slope guide 200 with an “L shape”configuration, rather than the “Z shape” configuration discussed above.Again, this construction provides several benefits. First, the “L shape”configuration permits guide element 215 to wrap around the perimeter ofthe tibia. Second, the “L shape” of guide element 215 also operates toindicate if the slope guide is not vertically aligned with the level ofthe fluoroscope. More particularly, if slope guide 200 is not verticallyaligned with the level of the fluoroscope, the “L shape” of guideelement 215 will appear as an “L shape” on the fluoroscope. However, ifguide element 215 is vertically aligned with the level of thefluoroscope, then the guide element will appear as a straight line onthe fluoroscope. Again, this vertical alignment is important, since itenables alignment of slope guide 200 (and hence positioning guide 100)with the medial condyle, i.e., with the A-P slope plane.

The assembly is then maneuvered so that the medial locating pin 140(FIGS. 10, 11 and 16), preferably formed as a pin although it could alsobe formed as a tab, fin, etc., is located against the medial aspect 80(FIG. 16) of the tibia. As further adjustments in position are made,medial locating pin 140 is held in contact with the medial aspect of thetibia, thereby ensuring proper alignment of the instrumentation. Mediallocating pin 140 references the medial aspect of the tibia, thus settingthe distance from the medial aspect of the tibia to the apex pin 300(FIG. 10), and hence the distance from the medial aspect of the tibia tothe axis 70 which demarcates the far limit of the osteotomy cut, as willhereinafter be discussed. Where a wedge-shaped osteotomy implant 27 isto be deployed in the wedge-like opening 25 (e.g., such as is shown inthe system of FIGS. 10-30), this reference distance is used inconjunction with the sizing of the osteotomy implant 27 (FIG. 3) so asto ensure a proper tibial reconstruction, e.g., the distance from themedial aspect of the tibia to the center of apex pin 300 may correspondto the distance from the medial aspect of the wedge-shaped osteotomyimplant 27 to the vertex of the wedge angle of the implant.

In another form of the invention, the reference distance may be thedistance from the medial aspect of the tibia to a neutral axis ofrotation in the bony hinge, which could be estimated by calculation. Inthis case, the distance from the medial aspect of the tibia to theneutral axis of the bony hinge may correspond to the distance from themedial aspect of the implant to the vertex of the wedge angle of theimplant.

The assembly is then rotated around the primary tibial anatomical axis,by sliding introducer handle 130 in a side-to-side motion, such that theinstrumentation is aligned perpendicular to the frontal (coronal) plane,i.e., so that introducer 105 and apex pin 300 (see below) will extendparallel to the sagittal plane of the patient. To this end, slope guide200 is provided with a ball 230 and a groove 235 (FIG. 10). With thefluoroscope arranged so that it is set in the lateral mode, with theimage being taken from the medial side at the level of the tibialplateau (see FIG. 11), the assembly is maneuvered until ball 230 iscentered in groove 235 (FIG. 11) this creates the ball and groovealignment sight 240. When this occurs, the system is aligned with thesagittal plane (i.e., positioning guide 100 is disposed so that apex pin300 will extend perpendicular to the frontal plane, as will hereinafterbe discussed).

Thus, when slope guide 200 is aligned with the medial condyle 75, andwhen ball 230 is aligned with groove 235, the system is aligned with (i)the A-P slope, and (ii) the sagittal plane. In other words, when slopeguide 200 is aligned with medial condyle 75, and when ball 230 isaligned with groove 235, the instrumentation is positioned so that apexpin 300 (see below) is aligned with both the A-P slope and the sagittalplane, as will hereinafter be discussed.

With all of the previous adjustments established, the positions of (i)tibial tubercle locating tab 135, (ii) slope guide 200, (iii) mediallocating pin 140, and (iv) the ball and groove sights 240 are verified.With all positions confirmed, the frontal pin 145 (FIG. 16) and theantero-medial (A-M) pin 150 (FIG. 16) are inserted through positioningguide 100 and into the tibia. This secures positioning guide 100 to thetibia with the desired alignment.

Next, apex pin 300 is inserted through positioning guide 100 and intothe tibia. An apex aimer 155 (FIGS. 14 and 16) serves to guide apex pin300 into the tibia with the proper orientation, i.e., so that apex pin300 is positioned along the axis 70 which is located at the laterallimit of the intended osteotomy cut, with apex pin 300 extendingparallel to the A-P slope and perpendicular to the coronal plane, andbeing coplanar with cutting plane 65. As a result, apex pin 300 canserve as the lateral stop for the osteotomy saw, whereby to clearlydefine the perimeter of the bony hinge, as will hereinafter bediscussed. Apex pin 300 may be tapped or drilled into virgin bone, or itmay be received in a pre-drilled hole (e.g., formed using apex aimer 155and a standard surgical drill). A thumbscrew 160 (FIG. 16) may be usedto secure apex pin 300 to positioning guide 100.

Apex pin 300 may be generally cylindrical in shape and, if desired, apexpin 300 may be provided with a rounded, or “bullet-shaped”, nose 303(FIG. 11G), or other tapered end configuration, so as to facilitatedeployment into the tibia.

Furthermore, if desired, apex pin 300 may have a flat 305 (FIGS. 12 and13) formed thereon to promote a complete cut-through of the osteotomycut 20. Where apex pin 300 is provided with a distinct flat 305, it ispreferably provided with a counterpart flat 310 (FIGS. 12 and 13), suchthat when apex pin 300 is positioned within the tibia and thumbscrew 160is tightened against flat 310, the aforementioned flat 305 will bealigned with the osteotomy cut, whereby to ensure that the osteotomyblade cuts completely through the bone to reach the apex pin. See FIG.13.

In another version of this construction (not shown), the flats 305, 310may be diametrically opposed to one another, with thumbscrew 160 alsobeing aligned with the osteotomy cut, whereby to make insertion of apexpin 300 less prone to error.

And in a preferred embodiment of the present invention, apex pin 300 maybe necked down to a smaller diameter in the area of the osteotomy. As aresult of this construction, a slight relief area exists to accommodatethe saw blade so as to help promote a complete cut-through, but does notrequire any specific orientation of the apex pin with respect to theosteotomy plane, as is the case where the apex pin is formed withdistinct flats.

And in another version of the present invention, apex aimer 155 may beused with an optional guide sleeve 161 (FIG. 14) and a small-diameterguide pin 165 in order to first check the position of the small-diameterguide pin 165 relative to the desired axis for the apex pin, beforethereafter deploying the larger-diameter apex pin 300. In this respect,it will be appreciated that repositioning a misdirected small-diameterguide pin 165 is easier and less traumatic to the host bone thanrepositioning a misdirected larger-diameter apex pin 300.

As seen in FIG. 15, tibial tubercle locating tab 135 is preferably sizedso that it also functions as an anterior protector, by providing aprotective shield between the oscillating saw blade (to be used later inthe procedure to form the osteotomy cut 20) and the anterior soft tissuestructures, e.g., the patellar tendon. In this respect it will berecalled that the tibial tubercle locating tab 135 is intended to bepositioned between the face of tibia 10 and the backside of the patellartendon. Thus, tibial tubercle locating tab 135 also functions as apatellar tendon protector.

By virtue of the foregoing, it will be seen that apex pin 300 ispositioned in the patient's tibia so that the apex pin extends (i)parallel to the A-P slope of the tibia, and (ii) parallel to thesagittal plane of the patient. As a result, when the osteotomy cut 20 issubsequently formed in the bone (see below) by cutting along theosteotomy cut plane (FIG. 8) until the apex pin is engaged by the bonesaw, so that the perimeter of the bony hinge is defined by the locationof the apex pin, the bony hinge will extend (i) parallel to the A-Pslope of the tibia, and (ii) parallel to the sagittal plane of thepatient. By ensuring that apex pin 300 is set in the aforementionedfashion, and hence ensuring that the bony hinge is so created, the finalconfiguration of the tibia can be properly regulated when the bone cutis thereafter opened so as to form the open wedge osteotomy.

As shown in FIG. 16, once apex pin 300 has been properly positioned inthe tibia 10, slope guide 200 and introducer 105 are removed, leavingpositioning guide 100 properly aligned on, and secured to, the tibia 10,with apex pin 300 extending parallel to the A-P slope and parallel tothe sagittal plane of the patient.

As will be discussed in further detail below, the system of FIGS. 10-30utilizes a wedge-shaped implant to maintain the open wedge osteotomy. Inthis respect, the size of positioning guide 100 and the associatedinstrumentation are preferably used to prepare the osteotomy to fit aparticular implant sizing of small, medium or large. More particularly,the medial locating pin 140, the size of positioning guide 100, and apexpin 300 all preferably combine to implement an implant sizing scheme ofsmall, medium or large. As seen in FIG. 17, medial locating pin 140,positioning guide 100 and apex pin 300 combine to provide a known, fixeddistance from the medial aspect of the tibia to the apex pin. The sizeof the planned osteotomy is then set, allowing a specifically-sizedimplant (e.g., small, medium or large) to nominally fit between themedial aspect of the tibia and the apex pin.

In the embodiment shown in FIG. 17, the position guide 100 possesses afixed distance for sizing 180 from the apex pin 300 to the mediallocating pin 140. In this embodiment, this creates known lateral offset175 between medial locating pin 140 and the entry point of the osteotomycut 20. The implant size is reduced slightly to factor in this offsetdistance so as to yield a proper fit.

In a more preferred construction, and looking now at FIG. 17A, mediallocating pin 140 is substantially aligned with the entry point of theplanned osteotomy, which eliminates the lateral offset 175.

Looking next at FIG. 18, keyhole drill guide 400 is then attached topositioning guide 100 by passing keyhole drill guide 400 over frontalpin 145 and apex aimer 155. Keyhole drill guide 400 is then secured inthis position with thumbscrew 405. At this point, a distal pin 410 isinserted through keyhole drill guide 400 and into the tibia. Distal pin410 further secures the instrumentation to the tibia. Next, a surfacelocator pin 415 is inserted through keyhole drill guide 400. Surfacelocator pin 415 slides through keyhole drill guide 400 until the distaltip of surface locator pin 415 contacts the surface of the tibia. Forthe purposes of the present invention, this surface may be referred toas the “antero-medial surface” or the “A-M surface”, which is theanatomical surface of the tibia corresponding to the antero-medialapproach of the osteotomy. When surface locator pin 415 contacts the A-Msurface, the surface locator pin can act as an indicator as to thelocation of the A-M surface. This information can then be used to setthe depth of the keyholes which are to be formed in the tibia (seebelow) for an improved implant fit.

Next, an end mill 420 is inserted into the distal hole 425 (i.e., thebottom hole 425) of keyhole drill guide 400 and drilled until a stopflange 430 on end mill 420 contacts the proximal end of surface locatorpin 415, whereby to form the distal keyhole 85 (FIG. 21) in the tibia.The drilling procedure is then repeated for the proximal hole 435 (i.e.,the top hole 435), whereby to form the proximal keyhole 90 (FIG. 21) inthe tibia. Thus, keyholes 85 and 90 are formed so that one keyhole(i.e., proximal keyhole 90) sits above the other keyhole (i.e., distalkeyhole 85), in a so-called “over-under” configuration. While it ispossible to drill the proximal keyhole before the distal keyhole, it isgenerally preferable to drill the distal keyhole first. This is becausedrilling the distal keyhole before the proximal keyhole reduces thepossibility that the sloping nature of the bone will cause alater-drilled keyhole to slip into an earlier-drilled keyhole. It shouldbe appreciated that keyhole drill guide 400 is configured so that distalhole 425 and proximal hole 435 will overlap the osteotomy cutting plane65 to some extent (FIG. 21), so that when osteotomy cut 20 is thereafterformed and the tibia subsequently opened so as to create the wedge-likeopening 25, distal keyhole 85 and proximal keyhole 90 will overlap, andcommunicate with, the wedge-like opening 25 (FIG. 29).

Once the two implant keyholes have been drilled into the tibia, end mill420 is removed, thumbscrew 405 is loosened, and then keyhole drill guide400 is removed.

Next, and looking now at FIG. 19, posterior protector 500 is attached toan introducer 505 with a thumbscrew 510, and handle 535. Posteriorprotector 500 preferably comprises a far tip 515 and a curved portion520. Far tip 515 is preferably formed out of a flexible material so asto facilitate passage of the posterior protector along the surface ofthe posterior cortex and beneath overlying soft tissue. Curved portion520 comprises a relatively stiff material which provides support for fartip 515. Far tip 515 of posterior protector 500 is inserted into theincision and worked along the posterior cortex of the tibia until fartip 515 of posterior protector 500 substantially crosses the axis of,and in some cases actually engages, apex pin 300 (FIG. 21). Onceposterior protector 500 has been properly deployed, the thumbscrew 510is unscrewed, and introducer handle 505 is removed, leaving posteriorprotector 500 extending along the posterior cortex of the tibia,interposed between the tibia and the delicate neurological and vascularstructures located at the back of the knee.

Looking next at FIGS. 20 and 21, cutting guide 600 is then attached topositioning guide 100 and secured in place using cutting guidethumbscrew 605. Cutting guide 600 comprises alignment features shown inFIGS. 20 and 21. These include alignment rods 610 that extend from thecutting guide into the pre-drilled keyholes 85, 90 to assist withcutting alignment. More particularly, alignment rods 610 ensure properalignment between cutting guide 600, its cutting slot 615 and thepre-drilled keyholes 85, 90 previously formed in the tibia with end mill420 and, ultimately, ensure the desired fit between the implant and thetibia.

Then, posterior protector 500 is attached to cutting guide 600 usingthumbscrew 620 (FIG. 20).

At this point, the instrumentation is ready to form the osteotomy cut,with cutting slot 615 of cutting guide 600 properly aligned with theosteotomy cut plane, apex pin 300 properly positioned at the far(lateral) limit of the osteotomy cut, tibial tubercle locating tab 135forming a protective shield for the patellar tendon, and with posteriorprotector 500 forming a protective shield for the vascular andneurological structures at the back of the knee. In this respect itshould be appreciated that cutting guide 600 is sized and shaped, andcutting slot 615 is positioned, so that, in addition to being alignedwith the apex pin 300, the entry point of the cutting plane into thetibia is located at an appropriate location on the tibia's medial neck66.

Next, a saw blade 625 (attached to an oscillating saw, not shown) isinserted into cutting slot 615 of cutting guide 600. The osteotomy cutis then made by plunging the oscillating saw blade through cutting slot615 and into the bone (FIG. 20). The saw blade is used to cut completelythrough the medial and posterior cortices. The saw is operated until sawblade 625 contacts posterior protector 500 and apex pin 300. As the sawblade cuts through the tibia, it is constrained by cutting slot 615,apex pin 300 and posterior protector 500, so that the saw blade may onlycut bone along the osteotomy plane, up to (but not beyond) the desiredlocation of the bony hinge, and does not cut soft tissue. Duringcutting, tibial tubercle locating tab 135 also ensures that the sawblade will not inadvertently cut the patellar tendon. Thus, cutting slot615, apex pin 300, posterior protector 500 and tibial tubercle locatingtab 135 effectively define a “safe cutting zone” for saw blade 625.

After saw blade 625 forms the desired osteotomy cut 20 along the cuttingplane, the saw blade is removed, and a hand osteotome (not shown) of thesort well know in the art is inserted through cutting slot 615 and intothe osteotomy cut 20, and then the cut is completed through theposterior cortical bone near apex pin 300 and posterior protector 500.Then the hand osteotome is removed.

At this point the osteotomy cut 20 has been completed, with theosteotomy cut terminating on the lateral side at apex pin 300, so thatthe bony hinge is properly positioned at the desired location, i.e.,parallel to the A-P slope and perpendicular to the coronal plane.

Next, thumbscrew 620 is loosened and posterior protector 500 removed.Then thumbscrew 605 is loosened and cutting guide 600 is removed. SeeFIG. 21.

At this point, the desired osteotomy cut 20 has been formed in thetibia, with keyholes 85 and 90 formed below and above, respectively, theosteotomy cut.

In order to complete the procedure, the bone must now be opened so as toreconfigure the tibia to the desired geometry, and then the tibiastabilized with the desired configuration, e.g., by inserting awedge-shaped implant 27 into wedge-like opening 25.

Looking next at FIG. 22, opening jack 700 is assembled onto theinstrumentation by receiving frontal pin 145 in a hole 705 formed injack arm 710, by receiving apex aimer 155 in another hole 715 formed injack arm 710 and jack arm 725, and by receiving distal pin 410 in a slot720 formed in jack arm 725. Opening jack 700 is secured to positioningguide 100 with a thumbscrew 730.

As is shown in FIG. 23, once opening jack 700 is in place, the jack isopened by rotating jack screw 735. This causes jack arm 725 to pivotabout apex aimer 155 so as to open the jack and thereby open the desiredwedge-like opening 25 in the tibia. Preferably the patient's lower legis manipulated as jack screw 735 is turned so as to assist in opening ofthe bone about the bony hinge. As the wedge-like opening 25 is createdin the bone, the tibia will be reoriented in a highly controlled manner,due to the fact that the bony hinge is precisely positioned at axis 70through the use of apex pin 300, i.e., the bony hinge will extendparallel to the A-P slope and parallel to the sagittal plane.Furthermore, as the wedge-like opening 25 is created in the bone, therisk of bone cracking is minimized, due to the fact that apex pin 300forms an oversized hole 95 (FIGS. 23A and 27) at the lateral end of thebone cut, i.e., “oversized” relative to the thickness of the osteotomycut, whereby to reduce the occurrence of stress risers and the like asthe bone is opened.

The surgeon uses opening jack 700 to open the bone to the extentnecessary to correctly re-align the weight-bearing axis of the knee.

Then, with opening jack 700 still in place, an implant is positioned inthe wedge-like opening 25 so as to hold the re-oriented bone with thedesired orientation.

If desired, the implant may be a “generic” wedge-shaped implant such asthe implant 27 shown in FIG. 3.

More preferably, however, and looking now at FIG. 24, there is shown awedge-shaped implant 800 formed in accordance with the presentinvention. Wedge-shaped implant 800 is characterized by a wedge-likeside profile configured to match the geometry of the wedge-like opening25 (i.e., to match the prescribed correction angle of the open wedge,high tibial osteotomy). Preferably, wedge-shaped implant 800 is alsoformed so as to have a U-shaped top profile, such that it can form abarrier about the perimeter of the wedge-like opening 25, with the openend of the U-shaped implant positioned against the bony hinge, wherebyto contain graft material (e.g., bone paste, bone cement, etc.) whichmay be positioned within the interior of the wedge-like opening 25. Inone preferred form of the present invention, wedge-shaped implant 800 isformed so as to have an asymmetric configuration when viewed in a topview, so as to mate with the geometry of the tibia when the implant ispositioned using an antero-medial approach. Wedge-shaped implant 800 issized so as to match the known distance from the medial aspect of thetibia to the axis 70 of the bony hinge, which is set by the position ofapex pin 300. Wedge-shaped implant 800 may be formed out of absorbablematerial or non-absorbable material, as desired.

In one preferred form of the invention, and looking now at FIGS. 25 and26, implant 800 preferably comprises a three-part assembly, comprisingposterior graft containment arm (GCA) 805, a base 810 and an anteriorgraft containment arm (GCA) 815. The individual components of implant800 may each be formed out of absorbable material and/or non-absorbablematerial, as desired. Furthermore, where one or more of the implantcomponents is formed out of an absorbable material, the absorptioncharacteristics of the material may vary as desired. By way of examplebut not limitation, base 810 may be formed out of a relativelyslowly-absorbing material, while posterior graft containment arm (GCA)805 and anterior graft containment arm (GCA) 815 may be formed out of arelatively faster-absorbing material. Base 810 preferably comprises apair of keys 820, 825. Keys 820, 825 have a disposition which iscomplementary to the disposition of the keyholes 85, 90, i.e., wherekeyholes 85, 90 have an “over-under” configuration, keys 820, 825 alsohave an “over-under” configuration, as will hereinafter be discussed infurther detail. In addition, the keys 820, 825 may be split to allow forexpansion, as shown by the split expansion anchor key 838.

In one preferred form of the invention, implant 800 is formed so thatposterior graft containment arm (GCA) 805 has a generally wedge-shapedprofile including an engagement seat 826 comprising an alignment post827, and an introducer hole 828 opening on the antero-medial side of thecomponent for engagement with introducer 845 (see below). Astrengthening rib 829 is preferably provided as shown. Additionally,raised points or dimples 831 may be provided to help fix posterior graftcontainment arm (GCA) 805 to the bone. An alignment tab 832 is providedfor extension into upper keyhole 90 (FIG. 29) when posterior graftcontainment arm (GCA) 805 is positioned in the wedge-shaped opening 25.

And in one preferred form of the invention, base 805 is formed so thatits keys 820, 825 each includes a bore 833, 834, respectively, with thekeys being slotted longitudinally so as to permit expansion of the keyswhen screws 865 are thereafter deployed in the bores, whereby to helplock the implant against the hard cortical bone of the tibia. Externalribs 836 may be provided on the outer surfaces of keys 820, 825 so as tohelp fix keys 820, 825 in keyholes 85, 90, respectively, when keys 820,825 are expanded, as will hereafter be discussed in further detail.External ribs 836 may extend longitudinally (FIG. 25) orcircumferentially (not shown). Keys 820, 825 protrude from the upper andlower surfaces of base implant 810, and accommodate shear loads whichmay be imposed across the implant. Furthermore, expansion of keys 820,825 creates an interference fit with the cortical bone of the tibia, andcan help support tensile loads which may be imposed across the implant.An alignment mechanism, e.g., a bore (not shown), is provided for matingwith alignment post 827 of posterior graft containment arm (GCA) 805.

The bores 833, 834 may be axially aligned with the longitudinal axes ofkeys 820, 825, respectively. Alternatively, the bores 833, 834 may bearranged so that they diverge from one another, downwardly and upwardly,respectively, so as to direct screws 865 deeper into the adjacentportions of the tibia.

Anterior graft containment arm (GCA) 815 also comprises a generallywedge-shaped profile, and an alignment tab 837 is provided for extensioninto lower keyhole 85 when GCA 815 is positioned in the wedge-shapedopening 25.

Implant 800 is preferably assembled in situ.

In some instances, it may be advantageous to use an implant trial base830 (FIGS. 27 and 28) in the course of preparing the tibia to receiveimplant 800, and in order to confirm proper fit of implant 800 in itsseat.

More particularly, a pre-assembled assembly comprising posterior graftcontainment arm (GCA) 805, an implant trial base 830 and two guidesleeves 835, 840 are first inserted into wedge-like opening 25 in thebone using an introducer 845. See FIGS. 27 and 28.

Next, a drill sleeve 850 and a drill 855 are inserted into guide sleeve840 (FIG. 27). An upper hole is drilled into the tibia with the drill.The drilling procedure is then repeated for guide sleeve 835 so as tocreate a lower hole. Then drill sleeve 850 and drill 855 are removedfrom the surgical site. Next, a tap 860 is inserted into guide sleeve840 and the upper hole is tapped. See FIG. 28. Then the tap is insertedinto guide sleeve 835 and the lower hole is tapped. Then tap 860 isremoved from the surgical site.

Next, posterior graft containment arm (GCA) 805 is released fromintroducer 845, and then introducer 845 and implant trial base 830 areremoved. Posterior graft containment arm (GCA) 805 remains in wedge-likeopening 25.

Then, if desired, graft material is packed into the osteotomy opening.

Next, anterior graft containment arm (GCA) 815 is placed into theosteotomy opening and aligned with the prepared implant holes. See FIG.29. If necessary, jack screw 735 is rotated as needed so as tofacilitate insertion of anterior GCA 815. At this point in theprocedure, posterior graft containment arm (GCA) 805 and anterior graftcontainment arm (GCA) 815 are positioned in wedge-like opening 25.

Then implant base 810 is inserted into the prepared osteotomy, with keys820 and 825 seated in tibial holes 85 and 90, respectively, and withbase 810 capturing posterior graft containment arm (GCA) 805 andanterior graft containment arm (GCA) 815 against the bony hinge. Keys820 and 825, seating in keyholes 85 and 90, help ensure a precise fit ofthe implant to the bone. As this is done, jack screw 735 is adjusted asnecessary so as to facilitate insertion of the base into the osteotomy.Then jack screw 735 is tightened slightly so as to ensure that theimplant components are fully seated into the osteotomy wedge, with atleast implant base 810, and preferably also posterior graft containmentarm (GCA) 805 and anterior graft containment arm (GCA) 815, providingload bearing support to the tibia. Next, fixation screws 865 areinserted through keys 820 and 825 in base 810 and into the tapped holesin the tibia, and then tightened into place. As this occurs, fixationscrews 865 expand keys 820, 825 so as to lock keys 820, 825 to theadjacent cortical bone, and fixation screws 865 extend into the tibia,so as to further lock the implant in position. See FIG. 30. Finally,opening jack 700, positioning guide 100, apex pin 300, distal pin 410,frontal pin 145 and A-M pin 150 are removed from the surgical site, andthe incision closed.

Providing implant 800 with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805 and anterior graft containment arm (GCA)815, is frequently preferred. However, in some circumstances, it may bedesirable to omit one or both of posterior graft containment arm (GCA)805 and anterior graft containment arm (GCA) 815. Thus, in one preferredform of the invention, implant 800 comprises only base 810 and omitsboth posterior graft containment arm (GCA) 805 and anterior graftcontainment arm (GCA) 815.

Providing implant 800 with a pair of keys 820, 825 is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820, 825. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820, 825 may include more than one bore833, 834. Thus, for example, a key may include two bores, one angledleftwardly so as to direct a fixation screw leftwardly into the tibia tothe left of the key, and/or one angled rightwardly so as to direct afixation screw rightwardly into the tibia to the right of the key.

The use of apex pin 300 is significant for a number of reasons:

(1) the oversized, circular diameter hole 95 (FIG. 23A) formed in thetibia by apex pin 300, which forms the limit of bone cut 20, effectivelydisplaces the stress forces created at the edge of the bony hinge whenthe cut is opened to form the wedge-like opening 25, thereby addingsignificantly to the effective strength of the bony hinge;

(2) by using apex pin 300 to control the length of bone cut 20 (asmeasured from the medial aspect of the tibia to the apex pin), the seatfor the implant is always of known size, thereby simplifying properfitting of the implant to its seat in the bone, and also reducing theinventory of different-sized implants which must be on hand during thesurgery;

(3) with apex pin 300 in place, bone resecting tools can be used withincreased confidence, without fear of inadvertently cutting into, oreven through, the bony hinge; and

(4) since apex pin 300 controls the depth of bone cut 20, the implantcan be reliably manufactured to appropriately address the requireddegree of correction needed to effect knee realignment (e.g., a 4 degreeimplant slope will always provide a 4 degree angle of correction).

Furthermore, the provision of (i) apex pin 300, posterior protector 500and tibial tubercle locating tab 135 creates a “protection zone”, and(ii) cutting guide 600 creates a closely constrained cutting path forsaw blade 625, thereby together ensuring that only the desired portionof the bone is cut. Among other things, the provision of posteriorprotector 500 ensures that the delicate neurological and vasculartissues at the back of the knee are protected during cutting of thetibia.

The provision of keyholes 85, 90 in the tibia, and the provision of keys820, 825 in the implant, is significant inasmuch as they provideimproved stabilization of the implant, particularly against rotationaland shearing forces. This is particularly true inasmuch as keyholes 85,90 extend through the hard cortical bone at the periphery of the tibia.

Implant with “Side-by-Side” Key Configuration

Looking next at FIGS. 31-33, there is shown an implant 800A also formedin accordance with the present invention. Implant 800A is generallysimilar to the implant 800 disclosed above, except that implant 800A hasits keys disposed in a “side-by-side” configuration, rather than the“over-under” key configuration of implant 800, as will hereinafter bediscussed in further detail. Furthermore, implant 800A also provides analternative approach for joining the posterior graft containment arm(GCA) to the base, and an alternative approach for joining the anteriorgraft containment arm (GCA) to the base, as will hereinafter also bediscussed in further detail.

More particularly, and still looking now at FIGS. 31-33, implant 800Acomprises a posterior graft containment arm (GCA) 805A, a base 810A andan anterior graft containment arm (GCA) 815A. Base 810A preferablycomprises a pair of keys 820A, 825A. Keys 820A, 825A are laterallydisplaced along the width of base 810A, in a “side-by-side”configuration. This is in contrast to the construction of implant 800,which uses an “over-under” configuration for its keys 820, 825 (FIG.24). Among other things, it has been found that the “side-by-side”configuration provides, at the base of the implant, excellentload-bearing characteristics and substantial resistance to rotationaland shear forces.

Posterior graft containment arm (GCA) 805A includes a tab 870A, and base810A includes a groove 873A, whereby posterior graft containment arm(GCA) 805A can mate with base 810A. A screw 875A is used to secure tab870A in groove 873A, and hence posterior graft containment arm (GCA) 805to base 810. Anterior graft containment arm (GCA) 815A includes a flange878A, and implant base 810A includes a recess 881A, whereby anteriorgraft containment arm (GCA) 815A can mate with base 810A. Another screw875A is used to secure flange 878A in recess 881A, and hence anteriorgraft containment arm (GCA) 815 to base 810. As is shown in FIG. 33, thetab 870A and groove 873A can be configured to interlock at theirinterface.

Posterior graft containment arm (GCA) 805A, and/or anterior graftcontainment arm (GCA) 815A, may include raised points or dimples 831A.

Keys 820A, 825A each include a bore 833A, 834A, respectively. Bores833A, 834A receive fixation screws 865A for fixing implant 800A to thetibia. Bores 833A, 834A preferably diverge from the longitudinal axes ofkeys 820A, 825A, respectively, so as to direct fixation screws 865Adownwardly or upwardly into the adjacent portions of the tibia. Keys820A, 825A may also include external ribs 836A. External ribs 836A mayextend longitudinally (not shown) or circumferentially (FIG. 32). Keys820A, 825A may also be slotted (i.e., in a manner analogous to the slotsprovided in keys 820, 825 of implant 800), whereby to permit keys 820A,825A to expand when fixation screws 865A are received in bores 833A,834A.

In order to provide appropriate keyholes 85A, 90A (FIG. 31) forreceiving keys 820A, 825A, a keyhole drill guide 400A (also sometimesreferred to as a “keystone drill template”) may be used (FIG. 34).Keyhole drill guide 400A is generally similar to the keyhole drill guide400 disclosed above, except that keyhole drill guide 400A has its twoguide holes 425A, 435A disposed in a “side-by-side” disposition, ratherthan the “over-under” disposition of the two guide holes 425, 435 ofdrill guide 400.

Implant 800A (and drill guide 400A) may be used in an open wedge, hightibial osteotomy in a manner which is generally similar to thatpreviously described with respect to implant 800 (and drill guide 400).

Providing implant 800A with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805A and anterior graft containment arm(GCA) 815A, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805A and anterior graft containment arm (GCA) 815A. Thus, in onepreferred form of the invention, implant 800A comprises only base 810Aand omits both posterior graft containment arm (GCA) 805A and anteriorgraft containment arm (GCA) 815A.

Providing implant 800A with a pair of keys 820A, 825A is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820A, 825A. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820A, 825A may include more than one bore833A, 834A. Thus, for example, a key may include two bores, one angledupwardly so as to direct a fixation screw upwardly into the tibia abovethe key, and/or one angled downwardly so as to direct a fixation screwdownwardly into the tibia below the key.

Implant with Alternative Approach for Joining Anterior Graft ContainmentArm (GCA) to Implant Base

Looking next at FIG. 35, there is shown another implant 800B also formedin accordance with the present invention. Implant 800B is generallysimilar to the implant 800A disclosed above, except that implant 800Bprovides an alternative approach for joining the anterior graftcontainment arm (GCA) to the implant base, among other things.

More particularly, and still looking now at FIG. 35, implant 800Bcomprises a posterior graft containment arm (GCA) 805B, a base 810B andan anterior graft containment arm (GCA) 815B. Base 810B preferablycomprises a pair of keys 820B, 825B. Keys 820B, 825B are laterallydisplaced along the width of base 810B, in a “side-by-side”configuration. Again, this is in contrast to the construction of implant800, which uses an “over-under” configuration for its keys 820, 825(FIG. 24).

Posterior graft containment arm (GCA) 805B includes a tab 870B, and base810B includes a groove 873B, whereby posterior graft containment arm(GCA) 805B can mate with base 810B. Anterior graft containment arm (GCA)815A includes a slide face 883B, and implant base 810B includes anopposing slide face 885B, whereby anterior graft containment arm (GCA)815B can mate with base 810B. A bridge-type fastener 888B is used tosecure anterior graft containment arm (GCA) 815B in position, with armslide face 883B engaging base slide face 885B, after the implant ispositioned within positioned within the wedge-like opening 25.

Posterior graft containment arm (GCA) 805B, and/or anterior graftcontainment arm (GCA) 815B, may include raised points or dimples 831B.

Keys 820B, 825B each include a bore 833B, 834B, respectively. Bores833B, 834B receive fixation screws 865B for fixing implant 800B to thetibia. Bores 833B, 834B preferably diverge from the longitudinal axes ofkeys 820B, 825B, respectively, so as to direct fixation screws 865Bdownwardly or upwardly into the adjacent portions of the tibia. Keys820B, 825B may also include external ribs 836B. External ribs 836B mayextend longitudinally or circumferentially. Keys 820B, 825B may also beslotted (i.e., in a manner analogous to the slots provided in keys 820,825 of implant 800), whereby to permit keys 820B, 825B to expand whenfixation screws 865B are received in bores 833B, 834B.

Implant 800B may be used in an open wedge, high tibial osteotomy in amanner which is generally similar to that previously described withrespect to implant 800.

Providing implant 800B with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805B and anterior graft containment arm(GCA) 815B, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805B and anterior graft containment arm (GCA) 815B. Thus, in onepreferred form of the invention, implant 800B comprises only base 810Band omits both posterior graft containment arm (GCA) 805B and anteriorgraft containment arm (GCA) 815B.

Providing implant 800B with a pair of keys 820B, 825B is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820B, 825B. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820B, 825B may include more than one bore833B, 834B. Thus, for example, a key may include two bores, one angledupwardly so as to direct a fixation screw upwardly into the tibia abovethe key, and/or one angled downwardly so as to direct a fixation screwdownwardly into the tibia below the key.

Implant with Shear Rib

Looking next at FIGS. 36-38, there is shown an implant 800C also formedin accordance with the present invention. Implant 800C is generallysimilar to the implant 800 disclosed above, except that implant 800C hasa shear rib 890C on its base, laterally displaced from the two keys(which are themselves arranged in an “over-under” configuration), aswill hereinafter be discussed in further detail. Furthermore, implant800C also provides an alternative approach for joining the posteriorgraft containment arm (GCA) to the base, and an alternative approach forjoining the anterior graft containment arm (GCA) to the base, as willhereinafter also be discussed in further detail. Furthermore, implant800C also provides a means for joining the distal end of posterior graftcontainment arm (GCA) 805C to the distal end of anterior graftcontainment arm (GCA) 815C, as will hereinafter also be discussed infurther detail.

More particularly, and still looking now at FIGS. 36-38, implant 800Ccomprises a posterior graft containment arm (GCA) 805C, a base 810C andan anterior graft containment arm (GCA) 815C. Preferably a bridge 892Cconnects the distal end of posterior graft containment arm (GCA) 805Cwith the distal end of anterior graft containment arm (GCA) 815C. Ifdesired, bridge 892C may be provided with a distal tab 898C to bereceived in oversized hole 95C. Distal tab 898C serves to improve thealignment and stability of implant 800C when seated in wedge-likeopening 25C. A shear rib 890C is formed in base 810C, laterallydisplaced from the two keys 820C, 825C, which are arranged in an“over-under” configuration.

Posterior graft containment arm (GCA) 805C includes a recess 893C, andbase 810C includes a shoulder 894C, whereby posterior graft containmentarm (GCA) 805C can mate with base 810C. Anterior graft containment arm(GCA) 815C includes a recess 895C, and implant base 810C includes ashoulder 896C, whereby anterior graft containment arm (GCA) 815C canmate with base 810C.

Posterior graft containment arm (GCA) 805C, and/or anterior graftcontainment arm (GCA) 815C, may include raised points or dimples 831C.

Keys 820C, 825C each include a bore 833C, 834C, respectively. Bores833C, 834C receive fixation screws 865C for fixing implant 800C to thetibia. The bores 833C, 834C may be axially aligned with the longitudinalaxes of keys 820C, 825C, respectively. Alternatively, the bores 833C,834C may be arranged so that they diverge from one another, downwardlyand upwardly, respectively, so as to direct screws 865C deeper into theadjacent portions of the tibia. Keys 820C, 825C may also includeexternal ribs 836C. External ribs 836C may extend longitudinally orcircumferentially. Keys 820C, 825C may also be slotted (i.e., in amanner analogous to the slots provided in keys 820, 825 of implant 800),whereby to permit keys 820C, 825C to expand when fixation screws 865Care received in bores 833C, 834C.

Shear rib 890C is laterally offset from keys 820C, 825C. Shear rib 890Cprojects above and below the top and bottom surfaces of base 810C. Amongother things, it has been found that the provision of shear rib 890Cprovides, at the base of the implant, excellent load-bearingcharacteristics and substantial resistance to rotational and shearforces.

In order to provide appropriate keyholes 85C, 90C (FIG. 36) forreceiving keys 820C, 825C, and also for providing a shear rib keyhole897C for receiving shear rib 890C, a keyhole drill guide 400C (alsosometimes referred to as a “keystone guide”) may be used (FIGS. 39 and40). Keyhole drill guide 400C is generally similar to the keyhole drillguide 400 disclosed above, except that keyhole drill guide 400C has, inaddition to its two guide holes 425C, 435C, a shear rib guidehole 440Cfor forming shear rib keyhole 897C. In addition, the keyhole drill guide400 may be provided an antero-medial surface locating point 485C and amedial locating pin 480C.

Implant 800C (and drill guide 400C) may be used in an open wedge, hightibial osteotomy in a manner which is generally similar to thatpreviously described with respect to implant 800 (and drill guide 400),except that the bridged graft containment unit, i.e., posterior graftcontainment arm (GCA) 805C, bridge 892C and anterior graft containmentarm (GCA) 815C, is installed as a single construction. Furthermore, whendrill guide 400C is used to form keyholes 85C and 90C, it is also usedto form shear rib keyhole 897C.

Providing implant 800C with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805C and anterior graft containment arm(GCA) 815C, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805C and anterior graft containment arm (GCA) 815C. Thus, in onepreferred form of the invention, implant 800C comprises only base 810Cand omits both posterior graft containment arm (GCA) 805C and anteriorgraft containment arm (GCA) 815C.

Providing implant 800C with a pair of keys 820C, 825C is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820C, 825C. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820C, 825C may include more than one bore833C, 834C. Thus, for example, a key may include two bores, one angledleftwardly so as to direct a fixation screw leftwardly into the tibia tothe left of the key, and/or one angled rightwardly so as to direct afixation screw rightwardly into the tibia to the right of the key.

If desired, shear rib keyhole 897C can be formed using a conventionaldrill. More preferably, however, and looking now at FIGS. 40 and 41,shear rib keyhole 897C is formed using a shear rib end mill 445C. Shearrib end mill 445C generally comprises a shaft 450C having cutting edges455C, a corner radius 460C and flutes 465C. A relief area 470C is formedjust proximal to corner radius 460C. An end stop 475C limits, throughengagement with drill guide 400C, the depth of shear rib keyhole 897C.

Implant with Expansion Thread Fixation Screws which Terminate within theKeys

Looking next at FIGS. 42-43, there is shown an implant 800D also formedin accordance with the present invention. Implant 800D is generallysimilar to the implant 800C disclosed above, except that implant 800D isintended to be used with expansion thread fixation screws that terminatewithin the keys. FIG. 44 shows the implant of FIGS. 42 and 43 incross-section as implanted into the prepared tibia.

More particularly, and still looking now at FIGS. 42-44, implant 800Dcomprises a posterior graft containment arm (GCA) 805D, a base 810D andan anterior graft containment arm (GCA) 815D. Preferably a bridge 892Dconnects the distal end of posterior graft containment arm (GCA) 805Dwith the distal end of anterior graft containment arm (GCA) 815D. Ifdesired, bridge 892D may be provided with a distal tab 898D to bereceived in oversized hole 95D. Distal tab 898D serves to improve thealignment and stability of implant 800D when seated in wedge-likeopening 25D.

A shear rib 890D is formed in base 810D, laterally displaced from thetwo keys 820D, 825D (which are themselves arranged in an “over-under”configuration). Posterior graft containment arm (GCA) 805D includes arecess 893D, and base 810D includes a shoulder 894D, whereby posteriorgraft containment arm (GCA) 805D can mate with base 810D. Anterior graftcontainment arm (GCA) 815D includes a recess 895D, and implant base 810Dincludes a shoulder 896D, whereby anterior graft containment arm (GCA)815D can mate with base 810D.

Posterior graft containment arm (GCA) 805D, and/or anterior graftcontainment arm (GCA) 815D, may include raised points or dimples 831D(not shown).

Keys 820D, 825D each include a bore 833D, 834D, respectively. Bores833D, 834D receive expansion thread fixation screws 865D for fixingimplant 800D to the tibia. Expansion thread fixation screws 865D areconfigured so as to intentionally terminate within bores 833D, 834D.This is in contrast to implant 800C which allows expansion threadfixation screws 865 to extend out of the distal ends of bores 833C, 834Cand then into the adjacent bone. The bores 833D, 834D may be axiallyaligned with the longitudinal axes of keys 820D, 825D, respectively.Keys 820D, 825D may also include external ribs 836D (not shown).External ribs 836D may extend longitudinally or circumferentially. Keys820D, 825D may also be slotted (i.e., in a manner analogous to the slotsprovided in keys 820, 825 of implant 800), whereby to permit keys 820D,825D to expand when expansion thread fixation screws 865D are receivedin bores 833D, 834D. The external thread on the expansion threadfixation screws 865D may be tapered so as to expand the bore into thecancellous bone of the tibia when the expansion thread fixation screwsare received within bores 833D, 834D. Alternatively, the internal threadon bores 833D, 834D may be tapered so as to expand the bore into thecancellous bone of the tibia when the expansion thread fixation screws865D are received within bores 833D, 834D.

Shear rib 890D is laterally offset from keys 820D, 825D, which arearranged in an “over-under” configuration. Shear rib 890D projects aboveand below the top and bottom surfaces of base 810D. Among other things,it has been found that the provision of shear rib 890D provides, at thebase of the implant, excellent load-bearing characteristics andsubstantial resistance to rotational and shear forces.

In order to provide appropriate keyholes 85D, 90D (FIG. 42) forreceiving keys 820D, 825D, and also for providing a shear rib keyhole897D for receiving shear rib 890D, a keyhole drill guide is used asdisclosed above.

Implant 800D (and an associated drill guide) may be used in an openwedge, high tibial osteotomy in a manner which is generally similar tothat previously described with respect to implant 800C (and drill guide400C), except that expansion thread fixation screws 865D terminatewithin bores 833D, 834D.

Providing implant 800D with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805D and anterior graft containment arm(GCA) 815D, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805D and anterior graft containment arm (GCA) 815D. Thus, in onepreferred form of the invention, implant 800D comprises only base 810Dand omits both posterior graft containment arm (GCA) 805D and anteriorgraft containment arm (GCA) 815D.

Providing implant 800D with a pair of keys 820D, 825D is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820D, 825D. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820D, 825D may include more than one bore833D, 834D. Thus, for example, one key may be expanded by multipleexpansion thread fixation screws 865D.

It should be noted that while the construction of implant 800D is highlysimilar to the construction of implant 800C, the construction of implant800D provides expansion thread fixation screws 865D that intentionallyterminate within bores 833D, 834D, and hence within the body of the key,i.e., they do not penetrate into the adjacent bone.

Implant with Draw Nuts

Looking next at FIGS. 45-46, there is shown an implant 800E also formedin accordance with the present invention. Implant 800E is generallysimilar to the implant 800C disclosed above, except that implant 800Eprovides counterbores 833EE, 834EE, respectively, for receiving drawnuts 867E, 868E, which in turn include bores 833EEE, 834EEE,respectively. FIG. 47 shows the implant of FIGS. 45 and 46 incross-section as implanted into the prepared tibia.

More particularly, and still looking now at FIGS. 45-47, implant 800Ecomprises a posterior graft containment arm (GCA) 805E, a base 810E andan anterior graft containment arm (GCA) 815E. Preferably a bridge 892Econnects the distal end of posterior graft containment arm (GCA) 805Ewith the distal end of anterior graft containment arm (GCA) 815E. Ifdesired, bridge 892E may be provided with a distal tab 898E to bereceived in oversized hole 95E. Distal tab 898E serves to improve thealignment and stability of implant 800E when seated in wedge-likeopening 25E.

A shear rib 890E is formed in base 810E, laterally displaced from thetwo keys 820E, 825E (which are themselves arranged in an “over-under”configuration). Posterior graft containment arm (GCA) 805E includes arecess 893E, and base 810E includes a shoulder 894E, whereby posteriorgraft containment arm (GCA) 805E can mate with base 810E. Anterior graftcontainment arm (GCA) 815E includes a recess 895E, and implant base 810Eincludes a shoulder 896E, whereby anterior graft containment arm (GCA)815E can mate with base 810E.

Posterior graft containment arm (GCA) 805E, and/or anterior graftcontainment arm (GCA) 815E, may include raised points or dimples 831E(not shown).

Keys 820E, 825E each include a bore 833E, 834E, respectively, and acounterbore 833EE, 834EE, respectively. Draw nuts 867E, 868E arepositioned at the distal ends of bores 833E, 834E, in counterbores833EE, 834EE, respectively. Draw nuts 867E, 868E each include a bore833EEE, 834EEE, respectively, such that when expansion thread fixationscrews 865E are received in bores 833E, 834E and bores 833EEE, 834EEE ofdraw nuts 867E, 868E, the draw nuts will be drawn into counterbores833EE, 834EE, thereby enhancing the expansion of keys 820E, 825E,whereby to securely fix implant 800E to the tibia.

The bores 833E, 834E may be axially aligned with the longitudinal axesof keys 820E, 825E, respectively. Keys 820E, 825E may also includeexternal ribs 836E (not shown). External ribs 836E may extendlongitudinally or circumferentially. Keys 820E, 825E may also be slotted(i.e., in a manner analogous to the slots provided in keys 820, 825 ofimplant 800), whereby to permit keys 820E, 825E to expand when expansionthread fixation screws 865E are received in bores 833E, 834E and inbores 833EEE, 834EEE of draw nuts 867E, 868E.

Shear rib 890E is laterally offset from keys 820E, 825E, which arearranged in an “over-under” configuration. Shear rib 890E projects aboveand below the top and bottom surfaces of base 810E. Among other things,it has been found that the provision of shear rib 890E provides, at thebase of the implant, excellent load-bearing characteristics andsubstantial resistance to rotational and shear forces.

In order to provide appropriate keyholes 85E, 90E (FIGS. 45 and 46) forreceiving keys 820E, 825E, and also for providing a shear rib keyhole897E for receiving shear rib 890E, a keyhole drill guide is used asdisclosed above.

Implant 800E (and an associated drill guide) may be used in an openwedge, high tibial osteotomy in a manner which is generally similar tothat previously described with respect to implant 800C (and drill guide400C). Providing implant 800E with two graft containment arms, e.g.,posterior graft containment arm (GCA) 805E and anterior graftcontainment arm (GCA) 815E, is frequently preferred. However, in somecircumstances, it may be desirable to omit one or both of posteriorgraft containment arm (GCA) 805E and anterior graft containment arm(GCA) 815E. Thus, in one preferred form of the invention, implant 800Ecomprises only base 810E and omits both posterior graft containment arm(GCA) 805E and anterior graft containment arm (GCA) 815E.

Providing implant 800E with a pair of keys 820E, 825E is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820E, 825E. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

Furthermore, each of the keys 820E, 825E may include more than one bore833E, 834E and counterbore 833EE, 834EE and more than one draw nut 867E,868E. Thus, for example, one key may be expanded by multiple expansionthread fixation screws 865E.

It should be noted that while the construction of implant 800E is highlysimilar to the construction of implant 800C, the construction of implant800E provides draw nuts 867E, 868E positioned at the distal ends ofbores 833E, 834E, received within counterbores 833EE, 834EE,respectively.

Implant with Open Keys

Looking next at FIGS. 48-50, there is shown an implant 800F also formedin accordance with the present invention. Implant 800F is generallysimilar to the implant 800C disclosed above, except that implant 800Fprovides open keys having opposed longitudinal edges. Furthermore, theopen keys include threaded recesses.

More particularly, and still looking now at FIGS. 48-50, implant 800Fcomprises a posterior graft containment arm (GCA) 805F, a base 810F andan anterior graft containment arm (GCA) 815F. Preferably a bridge 892Fconnects the distal end of posterior graft containment arm (GCA) 805Fwith the distal end of anterior graft containment arm (GCA) 815F. Ifdesired, bridge 892F may be provided with a distal tab 898F to bereceived in oversized hole 95F. Distal tab 898F serves to improve thealignment and stability of implant 800F when seated in wedge-likeopening 25F.

A shear rib 890F is formed in base 810F, laterally displaced from twoopen keys 820F, 825F (which are themselves arranged in an “over-under”configuration). Posterior graft containment arm (GCA) 805F includes arecess 893F, and base 810F includes a shoulder 894F, whereby posteriorgraft containment arm (GCA) 805F can mate with base 810F. Anterior graftcontainment arm (GCA) 815F includes a recess 895F, and implant base 810Fincludes a shoulder 896F, whereby anterior graft containment arm (GCA)815F can mate with base 810F.

Posterior graft containment arm (GCA) 805F, and/or anterior graftcontainment arm (GCA) 815F, may include raised points or dimples 831F(not shown).

Open keys 820F, 825F each include a threaded recess 833F, 834F,respectively. It should be appreciated that due to the geometry of theopen keys 820F, 825F when expansion thread fixation screws 865F arereceived in the threaded recesses 833F, 834F, a portion of the threadedsurface of expansion thread fixation screws 865F are exposed to, andhence directly engage, the adjacent bone. This is in contrast withimplant 800C, wherein the fixation screws 865C are received withinclosed keys 820C, 825C.

In one form of the present invention, the keyholes 85F, 90F may befurther prepared by tapping with a tap 899F (not shown) with acorresponding thread pitch to that of expansion thread fixation screws865F.

Threaded recesses 833F, 834F may be axially aligned with thelongitudinal axes of open keys 820F, 825F, respectively. Open keys 820F,825F may also include external ribs 836F. External ribs 836F may extendlongitudinally or circumferentially. Open keys 820F, 825F may also beonly partially opened, i.e., along only a portion of the length of thekeys (i.e., in a manner analogous to the slots provided in keys 820, 825of implant 800), whereby to provide open keys 820F, 825F with greaterstructural integrity.

Shear rib 890F is laterally offset from open keys 820F, 825F, which arearranged in an “over-under” configuration. Shear rib 890F projects aboveand below the top and bottom surfaces of base 810F. Among other things,it has been found that the provision of shear rib 890F provides, at thebase of the implant, excellent load-bearing characteristics andsubstantial resistance to rotational and shear forces.

In order to provide appropriate keyholes 85F, 90F (FIG. 48) forreceiving open keys 820F, 825F, and also for providing a shear ribkeyhole 897F for receiving shear rib 890F, a keyhole drill guide is usedas disclosed above.

Implant 800F (and the associated drill guide) may be used in an openwedge, high tibial osteotomy in a manner which is generally similar tothat previously described with respect to implant 800C (and drill guide400C), except that the bridged graft containment unit, i.e., posteriorgraft containment arm (GCA) 805F, bridge 892F and anterior graftcontainment arm (GCA) 815F, is installed as a single construction.Furthermore, when drill guide 400F is used to form keyholes 85F and 90F,it is also used to form shear rib keyhole 897F.

Providing implant 800F with two graft containment arms, e.g., posteriorgraft containment arm (GCA) 805F and anterior graft containment arm(GCA) 815F, is frequently preferred. However, in some circumstances, itmay be desirable to omit one or both of posterior graft containment arm(GCA) 805F and anterior graft containment arm (GCA) 815F. Thus, in onepreferred form of the invention, implant 800F comprises only base 810Fand omits both posterior graft containment arm (GCA) 805F and anteriorgraft containment arm (GCA) 815F.

Providing implant 800F with a pair of open keys 820F, 825F is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of open keys 820F, 825F. Furthermore, inother circumstances, it may be desirable to provide more than two openkeys, e.g., to provide three open keys.

Furthermore, each of the open keys 820F, 825F may include more than onethreaded recess 833F, 834F. Thus, for example, open keys may containmultiple, but not overlapping, recesses to receive multiple expansionthread fixation screws 865F. Thus, for example, an open key may includetwo recesses, one angled leftwardly so as to direct a fixation screwleftwardly into the tibia to the left of the open key, and/or one angledrightwardly so as to direct a fixation screw rightwardly into the tibiato the right of the open key.

It should be noted that while the construction of implant 800F is highlysimilar to the construction of implant 800C, the construction of implant800F provides keys which allow a portion of the threaded surface ofexpansion thread fixation screws 865F to directly engage the adjacentbone.

One-Piece Implant with Locking Fixation Screws

Looking next at FIGS. 51-56, there is shown an implant 800G also formedin accordance with the present invention. Implant 800G is generallysimilar to the implant 800A disclosed above, except that implant 800Gcomprises a one-piece implant with locking fixation screws, as willhereinafter be discussed in further detail. Furthermore, implant 800Geffectively omits the anterior and poster graft containment arms (GCAs),and essentially comprises just the implant base, as will hereinafteralso be discussed in further detail.

More particularly, and looking now at FIGS. 51-56, implant 800Gcomprises an implant base 810G. Base 810G preferably comprises a pair ofkeys 820G, 825G. Keys 820G, 825G are laterally displaced along the widthof base 810G, in a “side-by-side” configuration. This is in contrast tothe construction of implant 800, which uses an “over-under”configuration for its keys 820, 825 (FIG. 24). Among other things, ithas been found that the “side-by-side” key configuration provides, atthe base of the implant, excellent load-bearing characteristics andsubstantial resistance to rotational and shear forces. Base 810Gpreferably comprises serrations 826G for enhancing engagement betweenimplant 800G and the surrounding bone. Base 810G also preferablycomprises a medial tab 871G and a lateral tab 872G.

Keys 820G, 825G each include a pair of bores 833G′, 833G″ and 834G′,834G″, respectively. Bores 833G′, 833G″, 834G′ and 834G″ receive lockingfixation screws 865G for fixing implant 800G to the tibia. Bores 833G′and 833G″, and bores 834G′ and 834G″, preferably diverge from thelongitudinal axes of keys 820G, 825G, respectively, in the manner shownin FIGS. 51-56 so as to direct fixation screws 865G downwardly andupwardly into the adjacent portions of the tibia. Keys 820G, 825G mayalso include external ribs 836G. External ribs 836G may extendlongitudinally or circumferentially.

In order to provide appropriate keyholes 85G, 90G (FIG. 51) in tibia 10for receiving keys 820G, 825G, an appropriate keyhole drill guide (alsosometimes referred to as a “keystone drill template”) may be used. Theappropriate keyhole drill guide is generally similar to the keyholedrill guide 400 disclosed above, except that the appropriate keyholedrill guide has its two guide holes disposed in a “side-by-side”disposition, rather than the “over-under” key disposition of the twoguide holes 425, 435 of drill guide 400.

Implant 800G (and the appropriate drill guide) may be used in an openwedge, high tibial osteotomy in a manner which is generally similar tothat previously described with respect to implant 800 (and drill guide400).

Providing implant 800G with a pair of keys 820G, 825G is generallypreferred. However, in some circumstances, it may be desirable to omitone or the other, or both, of keys 820G, 825G. Furthermore, in othercircumstances, it may be desirable to provide more than two keys, e.g.,to provide three keys.

As noted above, each of the keys 820G, 825G includes more than one bore.Thus, for example, a key may include two bores, one angled upwardly soas to direct a fixation screw upwardly into the tibia above the key(i.e., 833G″ and 834G″), and/or one angled downwardly so as to direct afixation screw downwardly into the tibia below the key (i.e., 833G′ and834G′).

As is shown in FIGS. 53 and 55, a locking feature is preferably providedto releasably lock fixation screws 865G to implant 800G. In onepreferred form of the present invention, fixation screws 865G maycomprise protrusions 866G (FIGS. 53 and 55) for releasably seating indetents 867G (FIGS. 52 and 55) formed in implant 800G as the fixationscrews are advanced through the implant, whereby to releasably lockfixation screws 865G to the implant. The exemplary screw 865G, shown inFIG. 53 is demonstrated with a Hexalobe Drive (ASTM 543-02) 874G.

More particularly, each of the fixation screws 865G has a generallycylindrical head 868G having one or more circumferential protrusions866G. Preferably a circumferential recess 869G is formed in cylindricalhead 868G adjacent to circumferential protrusion 866G, in order topermit resilient deformation of the fixation screw's protrusion whilethe fixation screw is being seated in the implant (but before theprotrusion is seated in the implant detent). If desired, additionalcircumferential recesses 869G may also be provided at locations otherthan immediately adjacent to the circumferential protrusions 866G,whereby to provide additional resiliency to head 868G. The detents 867Gare formed in the base, in the sidewall which defines bores 833G′,833G″, 834G′ and 834G″. Detents 867G are sized so as to receive screwprotrusions 866G, whereby to releasably lock fixation screws 865G withinbores 833G′, 833G″, 834G′ and 834G″. Thus, in use, as fixation screws865G are advanced through bores 833G′, 833G″, 834G′ and 834G″, theirprotrusions 866G will seat in body detents 867G, whereby to releasablylock the fixation screws to the implant.

Fixation Screws for Improved Engagement with Both Cortical andCancellous Bone

Looking next at FIGS. 57-66, there is shown an improved combinationunicortical/cancellous bone fixation screw 865H for use with anosteotomy implant, e.g., implant 800H. Fixation screws 865H areconfigured for improved engagement with both cortical bone andcancellous bone, by providing two different segments of screw threadsalong the screw shaft, with each thread segment having different threadattributes.

More particularly, as seen in FIGS. 57 and 58, fixation screw 865Hcomprises a distal screw thread segment 870H which is characterized by arelatively fine thread pitch having a relatively shallow thread height,and a proximal screw thread segment 875H which is characterized by arelatively coarse thread pitch having a relatively high thread height.The combination unicortical/cancellous sore has the advantage ofallowing the thread to engage both the cortical and cancellous bone. Thefine pitch/shallow thread segment 870H on the distal end of the screwallows a higher thread density for engagement in hard cortical bone,which results in more threads engaged in the cortical bone. The coarsepitch/higher thread segment 875H allows greater thread penetration (ordepth) in the softer cancellous bone. Since the lead is the same on boththread profiles (i.e., distal thread segment 870H and proximal threadsegment 875H), fixation screw 865H can be advanced serially in bothtypes of bone (i.e., cortical bone and cancellous bone) withoutstripping either of the threads and, to the extent that the bone istapped, without stripping the internal threads of the tapped hole. Inexemplary FIG. 57, the screw 865H is shown with all threads having a 3.6mm lead. The proximal thread segment 875H is a single start with a 1.75mm pitch, while the distal thread segment 870H is a double start with a3.5 mm pitch.

FIGS. 59 and 60 illustrate a tap 965H which may be used to prepare thebone to receive fixation screw 865H. To this end, tap 965H comprises athread profile which substantially corresponds to the thread profile offixation screw 865H, i.e., it comprises a distal screw thread segment970H which is characterized by a relatively fine thread pitch having arelatively shallow thread height, and a proximal screw thread segment975H which is characterized by a relatively coarse thread pitch having arelatively high thread height. A cutting flute 980H extends throughdistal screw thread segment 970H and a portion of proximal screw threadsegment 975H whereby, when tap 965H is turned into bone, the desiredinternal thread will be created in the bone. The tap is illustrated witha double start tap at the distal end that possesses an exemplary leadand one-half the pitch of the tap segment proximal to it, which is forthe cancellous portion of the bone. Because the cortical thread is adouble-start with the same lead and half the pitch of the cancellousthread, the tap will advance simultaneously into both the cortical andcancellous bone at the same rate; however, the double start will allowmore threads to be engaged into the cortex.

FIGS. 61-63 show tap 965H extending through implant 800H and tappingtibia 10, whereby to provide a threaded seat for receiving fixationscrews 865H. As is shown in FIG. 61, the tap is used in conjunction withthe implant. The implant serves as a guide for the tap to ensure properplacement of the screws.

If desired, any number of fixation screws 865H may be used to secureimplant 800H in the bone. More particularly, FIGS. 64-66 show fourfixation screws 865H securing implant 800H to tibia 10.

It should be appreciated that distal screw thread segment 870H may beformed with a “double start” thread (i.e., two side-by-side singlethreads) in order to provide the variation in pitch between distal screwthread segment 870H and proximal screw thread segment 875H.

It should also be appreciated that fixation screws 865H (and implant800H) may be formed with or without the locking mechanism discussedabove with respect to the construction of FIGS. 51-56, i.e., protrusions866H for seating in implant detents 867H.

Anterio-Lateral Osteotomies

In the foregoing description, the present invention is discussed in thecontext of performing an open wedge osteotomy using an antero-medialapproach so as to effect a medial opening wedge osteotomy. Of course, itshould be appreciated that the present invention may also be used inantero-lateral approaches so as to effect a lateral opening wedgeosteotomy, or in other approaches which will be well known to thoseskilled in the art.

Modifications

It will be understood that many changes in the details, materials, stepsand arrangements of parts, which have been herein described andillustrated in order to explain the nature of the invention, may be madeby those skilled in the art without departing from the principles andscope of the present invention.

What is claimed is:
 1. Apparatus for performing an open wedge, hightibial osteotomy, the apparatus comprising: a wedge-shaped implant fordisposition in a wedge-shaped opening created in the tibia, wherein thewedge-shaped implant comprises at least one upwardly or downwardlyangled bore hole, the bore hole has an internal surface with a screwhead engaging detent adjacent a proximal end of the bore hole; adiscrete fixation screw for extending through the bore hole and securingthe wedge-shaped implant to the tibia comprising a fixation screw headand integral threaded shaft, the fixation screw head comprising an outercircumferential surface with at least one radially outwardly extendingprotrusion and at least one adjacent, radially inwardly extendingrecess; and a locking mechanism for releasably locking the discretefixation screw to the wedge-shaped implant, the locking mechanismcomprising the surface detent formed in the bore hole and the protrusionformed on the fixation screw head, such that the protrusion is capableof being seated in the detent if the fixation screw is advanced throughthe wedge-shaped implant.
 2. Apparatus according to claim 1 wherein thewedge-shaped body further comprises a key for disposition in acorresponding keyhole formed in the tibia adjacent to the wedge-shapedopening created in the tibia.
 3. Apparatus according to claim 2 whereinthe bore hole in the wedge-shaped implant is disposed in the key. 4.Apparatus according to claim 1 wherein the wedge-shaped body furthercomprises a pair of keys for disposition in a pair of correspondingkeyholes formed in the tibia adjacent to the wedge-shaped openingcreated in the tibia, a pair of bore holes wherein one bore hole isdisposed in each key, a pair of fixation screws wherein one screwextends through each bore hole, and locking mechanisms for releasablylocking the fixation screws to the wedge-shaped body.
 5. Apparatusaccording to claim 4 wherein the keys are laterally displaced from oneanother in an “over-under” configuration.
 6. Apparatus according toclaim 4 wherein the keys are laterally displaced from one another in a“side-by-side” configuration.
 7. The Apparatus according to claim 1,wherein the protrusion formed on the fixation screw is formed such thatit deforms when seated in the implant.
 8. Apparatus for performing anopen wedge, high tibial osteotomy, the apparatus comprising: a fixationscrew having a head and integral shaft for securing an implant to thetibia, the fixation screw wherein the head has a continuous, generallycylindrical outer circumferential surface with at least onelongitudinally arranged recess extending inwardly from the generallycylindrical outer circumferential surface, and at least one protrusion,extending outwardly from the generally cylindrical outer circumferentialsurface, wherein said recess is defined by being wholly within acircumference of said generally cylindrical outer circumferentialsurface and the at least one circumferentially located protrusionresiliently deforms; and the shaft has a distal threaded portion and aproximal threaded portion, wherein the distal threaded portion and theproximal threaded portion are characterized by different thread pitches.9. Apparatus according to claim 8 wherein the apparatus comprises aplurality of fixation screws.
 10. The Apparatus according to claim 8,wherein the at least one circumferentially located protrusion is formedadjacent to the at least one external circumferentially located recess.11. Apparatus for performing an open wedge, high tibial osteotomy, theapparatus comprising: a fixation screw having a head and integral shaftfor securing an implant to the tibia, the fixation screw wherein thehead has a continuous, generally cylindrical outer circumferentialsurface with at least one longitudinally arranged recess, located on thegenerally cylindrical outer circumferential surface, and at least oneprotrusion, located on the generally cylindrical outer circumferentialsurface and adjacent the at least one recess to provide resilientdeformation of the at least one protrusion, wherein said recess isdefined by being wholly within said circumference and said protrusionextends outwardly from said circumference and the at least onecircumferentially located protrusion resiliently deforms; and the shafthas a distal threaded portion and a proximal threaded portion, whereinthe distal threaded portion and the proximal threaded portion arecharacterized by different thread heights.
 12. The Apparatus accordingto claim 11, wherein the at least one circumferentially locatedprotrusion is formed adjacent to the at least one externalcircumferentially located recess.
 13. Apparatus according to claim 8wherein the distal threaded portion has a fine thread pitch with arelatively shallow thread height so as to engage cortical bone, and theproximal threaded portion has a coarse thread pitch having a relativelyhigh thread height so as to engage cancellous bone.
 14. Apparatus forperforming an open wedge, high tibial osteotomy, the apparatuscomprising: a wedge-shaped implant for disposition in a wedge-shapedopening created in the tibia, wherein the wedge-shaped implantcomprises: an upper surface; a lower surface; at least one key, whereinthe key comprises an outwardly directed surface that extends from atleast one of the upper and lower surfaces and is configured to seatwithin a correspondingly formed keyhole within the tibia; and a borehole extending through the at least one key for receiving a fixationscrew in an angularly upward or downward direction; a discrete fixationscrew for extending through the bore hole and securing the wedge-shapedimplant to the tibia comprising a fixation screw head and integralthreaded shaft, wherein the fixation screw head has an outer surfacewith at least one outwardly directed radial protrusion and at least oneinwardly directed radial recess adjacent to the protrusion; and alocking mechanism for releasably locking the fixation screw to thewedge-shaped implant, wherein the locking mechanism comprises a detentformed within a circumference of the bore hole of the wedge-shapedimplant and the protrusion formed on the fixation screw, such that theprotrusion is capable of being seated in the detent if the fixationscrew is advanced through the wedge-shaped implant.
 15. Apparatusaccording to claim 14 wherein the wedge-shaped implant furthercomprises: a second key extending from at least one of the upper orlower surfaces for disposition in a corresponding keyhole formed in thetibia adjacent to the wedge-shaped opening created in the tibia; and asecond bore hole disposed in the second key.
 16. Apparatus according toclaim 15 wherein the keys are displaced from one another in an“over-under” configuration.
 17. Apparatus according to claim 15 whereinthe keys are displaced from one another in a “side-by-side”configuration.